At the annual NICAR conventions, we do a lot of training for fellow journalists, and one of our standard spreadsheet exercises teaches students how to crunch numbers via some data on drug arrests in South Florida during the early 1990s -- hey, it's hard to find a good training data set.

The goal of this exercise is to teach students how to apply their new Excel skills to public records and turn up a nugget of information worth pursuing as a story. At the end of the hour, they discover that while South Florida drug arrests are way up, police are increasingly going after drug users, not the dealers.

We then teach them that they could use this analysis as a basis for raising the question of whether such police tactics are the most effective way of combating the drug problem.

In browsing through section 3, the state and county arrest summary, I came upon the drug arrest table and thought: "I've seen this trend before!"

Since 2002 in New Jersey, the arrest pattern has shifted significantly -- Dealers had accounted for nearly a third of arrests, but now account for less than a quarter over a time period in which the total number of arrests remained level.

Because we love context here at Stat Attack, I went back to the 2001 UCR and pulled the previous five years and found that the current trend is a reversal of the way the numbers had been trending over the previous three years.

In general, this type of pattern is driven by police resources. Going after drug dealers is more time intensive and expensive. Going after users is somewhat easier and helps keep the arrest stats high. Whether this explains the New Jersey numbers or not remains to be seen...